Commit df04abfd authored by Jiri Olsa's avatar Jiri Olsa Committed by Linus Torvalds

fs/proc/kcore.c: Add bounce buffer for ktext data

We hit hardened usercopy feature check for kernel text access by reading
kcore file:

  usercopy: kernel memory exposure attempt detected from ffffffff8179a01f (<kernel text>) (4065 bytes)
  kernel BUG at mm/usercopy.c:75!

Bypassing this check for kcore by adding bounce buffer for ktext data.
Reported-by: default avatarSteve Best <>
Fixes: f5509cc1 ("mm: Hardened usercopy")
Suggested-by: default avatarKees Cook <>
Signed-off-by: default avatarJiri Olsa <>
Acked-by: default avatarKees Cook <>
Signed-off-by: default avatarLinus Torvalds <>
parent f5beeb18
......@@ -509,7 +509,12 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
if (kern_addr_valid(start)) {
unsigned long n;
n = copy_to_user(buffer, (char *)start, tsz);
* Using bounce buffer to bypass the
* hardened user copy kernel text checks.
memcpy(buf, (char *) start, tsz);
n = copy_to_user(buffer, buf, tsz);
* We cannot distinguish between fault on source
* and fault on destination. When this happens
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